1. Field of the Invention
The present invention relates to exercise monitors and other devices operable to determine a distance traveled by a user. More particularly, the invention relates to an electronic distance-measuring device for use during exercising, walking, running, etc. and operable to determine a distance traveled by the user. The electronic device includes a location determining component, such as a global positioning system (“GPS”) device, a pedometer, and a computing device operable to accurately determine the distance traveled, even if the user's step size changes during an exercise session due to changes in speed, altitude, etc.
2. Description of the Prior Art
Pedometers have long been used by fitness enthusiasts to determine a distance traveled during walking, running, hiking, etc. Prior art pedometers are commonly small in size and wearable on the user's body so as to sense steps taken by the user. In particular, pedometers are operable to sense the up/down movement of the user when walking, running, etc., such that each sensed movement corresponds to a step traveled. The distance traveled is then calculated by multiplying the number of steps traveled by an estimated step size of the user. Therefore, the distance traveled is significantly dependent on the user's step size or stride length.
To account for the user's step size, prior art pedometers provide several options for initially calibrating the pedometer. One such option requires the user to input the user's height. A data table providing average step size for a plurality of height ranges is then accessed to determine the average step size for users having the user's height. As can be appreciated, the data tables only reflect the average step size and offer no step size measurements individualized for the particular user.
A second initial calibration option requires the user to travel a known distance and count the number of steps to cover such distance. The user then inputs the number of steps into the pedometer and the pedometer uses a basic mathematical algorithm to determine the user's step size. The user must first, however, correctly measure the known distance, and second, the user must cover the distance at the general pace or speed the user will be traveling when using the pedometer.
A third option requires the user to set up a puddle of water, begin traveling well before reaching the puddle of water, such that when the user reaches the puddle of water, the user is traveling at his/her preferred speed, step into the puddle so as to wet the user's feet, step out of the puddle onto dry concrete or other surface that allows the user's footprints to be viewed, and measure the wet footprints from toe to heel to determine the user's step size.
Unfortunately, even if the user correctly initially calibrates the pedometer, pedometers are limited in determining the distance traveled if the step size of the user changes during the measurement period or if the pedometer senses extraneous movement of the user that does not actually correspond to a moved step of the user. Because the pedometer calculates the distance traveled by multiplying the number of steps taken by the step size, variations in the user's step size greatly affect the measured distance traveled. Over time, these errors can accumulate to incorrectly affect the measured distance traveled by as much as 10-20%, especially if the user changes his or her step size due to changes in a moving pace from walking, running, or sprinting. Additionally, the user may change his or her step size when changing altitudes, such as during hiking uphill/downhill.
To compensate for the disadvantages of prior art pedometers, electronic distance measuring devices have been configured that include both the pedometer and an accelerometer. An accelerometer senses an acceleration force of the user resulting from the user's impact with the ground due to walking, running, hiking, etc. The acceleration force may be detected by numerous means, including detection of a change in the electrical resistance of a flexure or measurement of a displacement of a silicon mass. The acceleration force of the user is translated into a step size of the user, which is then used to determine the distance traveled.
Although accelerometers provide a mechanism for determining the user's step size, accelerometer measurements are not always accurate or consistent. The accelerometers may still sense other movement of the user not associated with actual traveled steps, such as if the user sits down in a chair or switches body weight while standing. Additionally, the accelerometer provides no initial calibration of the pedometer, thus still requiring the user to initially calibrate the pedometer so as to have a general “zeroing” or base value for the user's step size.
Even with the disadvantages of both pedometers and accelerometers, they have been used in location determining systems to provide dead reckoning functions. The location determining systems commonly use a global positioning system (“GPS”) receiver to determine or calculate a location or a position of a user. However, the GPS receiver is not always operable when GPS satellite signals are blocked by heavily wooded areas, tall buildings, tunnels, etc. The location determining systems compensate for the inaccessibility of GPS satellite signals by providing the pedometer and/or accelerometer, which are operable to determine the distance traveled from a previously known location. However, as discussed above, the pedometer and/or accelerometer are not consistently accurate, thus causing error to accumulate when the pedometer and/or accelerometer are the sole location determining components of the location determining system. Therefore, when GPS satellite signals are again accessible, the GPS receiver corrects the accumulated error of the pedometer and/or accelerometer.
Prior art location determining systems comprising the GPS receiver and the pedometer and/or accelerometer are not configured to calculate a distance traveled but rather are configured to determine the location or position of the user. As such, the systems provide no method or mechanism for calibrating the pedometer so that the pedometer may calculate a more accurate distance traveled. Instead, the systems merely correct accumulated position error once GPS satellite signals are accessible, which does not allow the pedometer to accurately determine the distance traveled at future times when GPS satellite signals are again inaccessible.
Accordingly, there is a need for an improved distance-measuring device that overcomes the limitations of the prior art. More particularly, there is a need for a device that will accurately determine a distance traveled, even when a location determining component of the device is inaccessible. Additionally, there is a need for a device that does not require initial calibration of the user's step size. Further, there is a need for a device that can learn the user's step size for varying speeds based upon past use by the user, such that the device is operable to determine the distance traveled, irrespective of whether the location determining component is accessible.